Real-time measurement of biaxial tensions using digital image correlation methods

The mechanical properties of biological materials need to be measured for various applications. A means of inducing biaxial tensions in samples like these is with an inflation or bulge test. Normally the material under test would be measured with displacement gauges, however, under these conditions, where the specimen is soft and further, where the measurement cycle cannot be reliably paused, a contactless real-time measurement system is necessary to obtain reliable deformation data. Digital Image Correlation (DIC) is one such method. Pioneered in the 1980s the field has developed from basic 2D displacement measurements to very sophisticated full field 3D displacement measurement systems. The question becomes can the current state of the field, as well as the advances in modern technology, be leveraged to create a useable 3D DIC measurement system that is: • Useable in a real-time context. • Portable enough to be able to run these experiments wherever the experiment apparatus is located. • Cost effective enough to reduce the barrier to entry that the current commercial options present. To this end off-the-shelf components were acquired to form the technology base of the system. The open-source DICe framework, which enabled the necessary level of access to the underlying code base, was implemented on an NVIDIA Jetson Nano single board computer. Synchronised, stereo image acquisition was implemented via an Arducam 12 MP camera system. A stepper motor controlled linear drive was used to experimentally investigate accuracy and speed of the DIC system, for both rigid body motion and deforming targets. A thorough review of the concepts involved in DIC is undertaken followed by a detailed description of the design and build of the system. Ultimately a set of experiments are executed that show that, within a set of important constraints, it is indeed possible to run 3D DIC in real-time with off the shelf, cost effective components.

Grantor

Department of Mechanical Engineering

Year dc:date.issued

2022

Author dc:creator

• Kyd, Haemish

Advisors dc:contributor.advisor

• Govender, Reuben Ashley
• Nicolls, Frederick

• Mechanical Engineering

Handle dc:identifier.uri

http://hdl.handle.net/11427/37831

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/37831